In general, a HMI (Human Machine Interface) device or panel PC means a multifunctional control device in a form of a panel excluding integrated mechanical elements such as a hard disk, a CD driver, a cooling fan, etc. such that the device may be easily used by a field worker.
The HMI device is provided in various forms including a fixed panel form in which the device may be fixed to a panel and a removable panel form in which the operator removes the device from the panel.
FIG. 1 shows a conventional coupling structure for an electronic device. FIG. 2 shows another conventional coupling structure for an electronic device.
As shown in FIG. 1, when installing an electronic device 5 such as an HMI device or panel PC, an operator first inserts the electronic device 5 into a mounting hole 2 defined in an outer casing 1. Thereafter, a hook-shaped bracket 7 formed on the electronic device 5 is hooked into the outer casing 1. Thus, the electronic device 5 may be prevented from being separated from the outer casing 1. In this connection, the bracket 7 is made of plastic. The hook-shaped portion passes through a hole defined in a front cover or rear cover of the electronic device 5 and is inserted into the hole 2 and caught into the outer casing 1. Further, the front or rear cover is detachable. An unexposed portion of the bracket 7 may be typically composed of 3 to 5 coupling parts such as springs, pins, and the like.
Alternatively, as shown in FIG. 2, for assembling an electronic device 5′, a bracket 7′ having a plurality of hooks is mounted between a front cover 5a or a rear cover 5b. Then, the front cover 5a and the rear cover 5b are coupled with each other via separate fastening bolts. The electronic device 5′ is then installed onto the outer casing 1. In this case, a construction and material of the bracket 7′ are the same as in FIG. 1.
However, since the conventional bracket for the electronic device is made of a plastic material, there is a risk that the hook-shaped portion of the bracket is bent or broken when the bracket is inserted into the mounting hole in the outer casing. Since the hook-shaped bracket is composed of the 3 to 5 parts, the assembling process is complicated and the cost of the bracket is increased.
Further, for an electronic device without a hook-shaped bracket, while one operator must keep a state in which the electronic device is inserted into the outer casing, another operator must work to fix the electronic device onto a back of the outer casing. Therefore, it is difficult to install the electronic device by one operator. Further, the assembling time is extended.